Method for preparation of medetomidine with chloroacetone

ABSTRACT

The invention discloses a method for the preparation of medetomidine starting from 1-bromo 2,3-dimethylbenzene and chloroacetone.

This application is a divisional application of U.S. application Ser.No. 14/385,797 having a filing date of Sep. 17, 2014, which is anational stage entry of International Patent Application No,PCT/EP2012/072798 having a filing date of Nov. 15, 2012, which claimsthe filing benefit of European Patent Application No. 12192625.7, havinga filing date of Nov. 14, 2012, International Patent Application No.PCT/EP2012/070875, having a thin date of Oct. 22, 2012, European PatentApplication No. 12188104.9, having a filing date of Oct. 11, 2012, U.S.Provisional Application No. 61/665,510, having a filing date of Jun. 28,2012, and European Patent Application No. 12174102.9, having a filingdate of Jun. 28, 2012, all of which are incorporated herein by referencein their entirety.

The invention discloses a method for the preparation of medetomidinestarting from 1-bromo 2,3-dimethylbenzene and chloroacetone.

Medetomidine is the compound of formula (XX) and is an alpha2 adrenergicagonist, which is currently being used as veterinary sedative andanalgesic and is evaluated as anesthetic.

Medetomidine is a 4-alkylimidazole. 4-Alkylimidazoles without additionalsubstituents at the nitrogen moiety are usually mixtures of twotautomers. For instance, in the case of medetomidine, two tautomericforms, represented by compound of formula (XX) and compound of formula(XX-T),

will usually interconvert if medetomidine is dissolved or in anon-crystalline state. If one of the tautomeric forms prevails or ifthey are present in equal amounts is dependent on various factors, suchas pH, solvent or temperature.

In the text, formula (XX) is used for medetomidine, and is meant tocomprise both tautomeric forms as well as their mixture.

US 2010/0048915 A discloses a method for the preparation of medetomidineby reaction of halogenated imidazoles with 2,3-dimethylbenzaldehydeusing Grignard reagents. Cordi et al, Synth. Commun. 1996, 26,1585-1593, discloses the preparation of medetomidine by reaction of4-imidazolcarboxaldehyde with 2,3-dimethylphenylmagnesium bromide.

WO 00/42851 A discloses the use of medetomidine for inhibition of marinebio fouling on surfaces.

The known methods of preparation of compound of formula (XX) often useprotecting groups, for example triphenylmethyl (trityl) residues, whichentails high material consumption and the need forprotection/deprotection steps. Consequently, these syntheses are longand expensive. Furthermore rather expensive and non-readily availablestarting materials are used.

There was a need for a synthetic route, which does not need protectinggroups, starts with less expensive substrates, avoids large amounts ofwaste and has satisfying yields.

In the following text,

-   halogen means F, Cl, Br or I, preferably Cl, Br or I;-   “alkyl” means linear, branched, cyclic or cyclo alkyl, preferably it    means the commonly accepted meaning linear or branched alkyl; if not    otherwise stated. Examples of “alkyl” include methyl, ethyl,    n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl,    heptyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,    cycloheptyl, norbornyl, adamantyl, and the like;-   “cyclic alkyl” or “cyclo alkyl” are intended to include cyclo    aliphatic, bicyclo aliphatic and tricycle aliphatic residues;-   “alkane” means a linear, branched or cyclic alkane, preferably    linear or branched alkane;-   “alkanol” means a hydroxy alkane, with alkane having the meaning as    defined above also with its preferred embodiments;-   Ac acetyl;-   tBu tertiary butyl;-   DBU 1,8-diazabicyclo[5.4.0]undec-7-ene;-   DABCO 1,4-diazabicyclo[2.2.2]octane;-   DMF N,N-dimethylformamide;-   hexanes mixture of isomeric hexanes;-   NMP N-methyl-2-pyrrolidone;-   OTf trifluoromethanesulfonate, also known as triflate;-   sulfamic acid HO—SO₂—NH₂;-   THF tetrahydrofuran;-   xylene 1,2-dimethylbenzene, 1,3-dimethylbenzene, 1,4-dimethylbenzene    or a mixture thereof;

if not otherwise stated.

Subject of the invention is a method for preparation of compound offormula (XX);

-   the method comprises four steps, the four steps are a step (Q1), a    step (Q2), a step (N) and a step (M1);-   compound of formula (XX) is prepared in step (M1);-   step (M1) comprises a reaction (M1-reac);-   reaction (M1-reac) is a reaction between a compound of formula    (XXI),

-   a reagent (M-reag) and a reagent (M-A) in a solvent (M-solv);-   reagent (M-reag) is selected from the group consisting of    p-toluenesulfonylmethyl isocyanide, trifluoromethanesulfonylmethyl    isocyanide, methanesulfonylmethyl isocyanide, benzenesulfonylmethyl    isocyanide, 4-acetamidobenzenesulfonylmethyl isocyanide and mixtures    thereof;-   reagent (M-A) is selected from the group consisting of ammonia,    sulfamic acid, p-toluenesulfonamide, benzenesulfonamide,    4-acetamidobenzenesulfonamide, tritylamine, formamide, urea,    urotropine, ethyl carbamate, acetamide and mixtures thereof;-   solvent (M-solv) is selected from the group consisting of    N,N-dimethylformamide, C₁₋₆ alkanol, formamide, 1,2-dimethoxyethane,    NMP, toluene, acetonitrile, propionitrile, ethyl carbamate,    N,N-dimethylacetamide, water, acetamide and mixtures thereof;-   compound of formula (XXI) is prepared in step (N);-   step (N) comprises a reaction (N-reac);-   reaction (N-reac) is a reaction of a compound of formula (XXII) with    a catalyst (N-cat);

-   catalyst (N-cat) is selected from the group consisting of acetic    acid, formic acid, trifluoroacetic acid, methanesulfonic acid,    benzenesulfonic acid, p-toluenesulfonic acid, camphorsulfonic acid,    HCl, HBr, H₂SO₄, HNO₃, H₃PO₄, HClO₄, BCl₃, BBr₃, BF₃OEt₂, BF₃SMe₂,    BF₃THF, MgCl₂, MgBr₂, Mgl₂, AlCl₃, Al(O—C₁₋₄ alkyl)₃, SnCl₄, TiCl₄,    Ti(O—C₁₋₄ alkyl)₄, ZrCl₄, Bi₂O₃, BiCl₃, ZnCl₂, PbCl₂, FeCl₃, ScCl₃,    NiCl₂, Yb(OTf)₃, Yb(Cl)₃, GaCl₃, AlBr₃, Ce(OTf)₃, LiCl, Cu(BF₄)₂,    Cu(OTf)₂, NiBr₂(PPh₃)₂, NiBr₂, NiCl₂, Pd(OAc)₂, PdCl₂, PtCl₂, InCl₃,    acidic inorganic solid substance, acidic ion exchange resin, carbon    treated with inorganic acid and mixtures thereof;-   step (Q1) comprises a reaction (Q1-reac);-   reaction (Q1-reac) is a reaction of compound of formula (XXV) with a    reagent (Q1-reag);

-   R1 is Br, Cl, or I;-   reagent (Q1-reag) is selected from the group consisting of lithium,    magnesium, aluminum, zinc, calcium, propylmagnesium chloride,    propylmagnesium bromide, butyllithium and mixtures thereof;-   step (Q2) comprises a reaction (Q2-reac);-   reaction (Q2-reac) is a reaction of the reaction product of reaction    (Q1-reac) with chloroacetone;-   compound of formula (XXII) is prepared by the reaction (Q2-reac).-   Preferably, reagent (M-reag) is selected from the group consisting    of p-toluenesulfonylmethyl isocyanide, benzenesulfonylmethyl    isocyanide and mixtures thereof;-   more preferably, reagent (M-reag) is p-toluenesulfonylmethyl    isocyanide.-   Preferably, reagent (M-A) is selected from the group consisting of    ammonia, sulfamic acid, p-toluenesulfonamide, benzenesulfonamide,    4-acetamidobenzenesulfonamide, tritylamine, formamide and mixtures    thereof;-   more preferably, reagent (M-A) is selected from the group consisting    of ammonia, p-toluenesulfonamide, benzenesulfonamide, formamide,    4-acetamidobenzenesulfonamide, tritylamine and mixtures thereof;-   even more preferably, reagent (M-A) is selected from the group    consisting of ammonia, p-toluenesulfonamide, formamide, and mixtures    thereof;-   especially, reagent (M-A) is ammonia or formamide.-   Preferably, reaction (M1-reac) is done in the presence of a compound    (M-comp), compound (M-comp) is selected from the group consisting of    ammonia, tritylamine, NaCN, KCN, piperidine, DBU, DABCO,    triethylamine, tributylamine, 4-dimethylaminopyridine, pyridine,    tBuOK, tBuONa, NaHCO₃, Na₂CO₃, (NH₄)HCO₃, (NH₄)₂CO₃, KHCO₃, K₂CO₃,    NaOAc, KOAc, NaOH, KOH, Ca(OH)₂, KF and mixtures thereof;-   preferably, compound (M-comp) is selected from the group consisting    of ammonia, tritylamine, NaCN, KCN, piperidine, tBuOK, tBuONa, KOH,    K₂CO₃, Na₂CO₃, KF and mixtures thereof;-   more preferably, compound (M-comp) is selected from the group    consisting of ammonia, NaCN, KCN, piperidine, tBuOK, tBuONa, K₂CO₃,    Na₂CO₃, KF and mixtures thereof;-   even more preferably, compound (M-comp) is selected from the group    consisting of ammonia, NaCN, K₂CO₃, tBuOK, tBuONa, Na₂CO₃ and    mixtures thereof;-   especially, compound (M-comp) is selected from the group consisting    of ammonia, NaCN, tBuOK, tBuONa, K₂CO₃, Na₂CO₃ and mixtures thereof;-   more especially, compound (M-comp) is K₂CO₃, Na₂CO₃, NaCN or    ammonia;-   even more especially, compound (M-comp) is Na₂CO₃, NaCN or ammonia.-   Preferably, solvent (M-solv) is selected from the group consisting    of N,N-dimethylformamide, methanol, ethanol, n-propanol,    isopropanol, butanol, pentanol, hexanol, water, formamide,    1,2-dimethoxyethane, NMP, toluene, acetonitrile, propionitrile,    ethyl carbamate, N,N-dimethylacetamide, acetamide and mixtures    thereof;-   more preferably, solvent (M-solv) is selected from the group    consisting of N,N-dimethylformamide, methanol, ethanol, ethyl    carbamate, formamide, acetamide and mixture thereof.

The reagent (M-A) can be used as such or in form of a solution in asolvent (M-A). Solvent (M-A) is identical or different from solvent(M-solv), preferably identical, and comprises the same group of solventsas solvent (M-solv), also with respect to all of the preferredembodiments of solvent (M-solv).

When reagent (M-A) is ammonia, then reagent (M-A) is preferably used inform of a solution, preferably in form of a solution in methanol orethanol.

In case of ethyl carbamate, formamide and acetamide, reagent (M-A) canbe identical with solvent (M-solv) and can be used as solvent (M-solv).

Preferably, the reaction temperature of reaction (M1-reac) is from −10to 250° C., more preferably from 0 to 200° C., even more preferably from10 to 180° C.

The reaction (M1-reac) can be done in a system, that is closed or opento the atmosphere; preferably the reaction (M1-reac) is done in a closedsystem.

-   In a closed system, the pressure depends mainly on the boiling point    of the solvent (M-solv), on the amount of ammonia used, and on the    reaction temperature of reaction (M1-reac);

preferably, the reaction (M1-reac) is done at a pressure of fromatmospheric pressure to 20 bar, more preferably of from atmosphericpressure to 10 bar, even more preferably of from atmospheric pressure to5 bar.

Preferably, the reaction time of reaction (M1-reac) is from 30 min to 72h, more preferably from 30 min to 48 h, even more preferably from 30 minto 24 h. Reaction (M1-reac) may be conducted at a constant temperature,or the temperature may be modified during the progress of the reaction.For instance, the reaction may be run for a certain time at firsttemperature, and then for a given time at second temperature differentfrom the first temperature;

alternatively, the temperature may be modified continuously during thereaction.

Preferably, from 0.5 to 10 mol equivalents, more preferably from 0.5 to5 mol equivalents, even more preferably from 0.5 to 3 mol equivalents ofreagent (M-reag) are used, the mol equivalents being based on the mol ofcompound of formula (XXI).

When one or more reagents (M-A) different from ammonia, formamide andethyl carbamate are used, the total amount of substances different fromammonia, formamide and ethyl carbamate used as reagent (M-A) ispreferably from 1.0 to 10 mol equivalents, more preferably from 1.1 to 5mol equivalents, even more preferably from 1.1 to 3 mol equivalents, themol equivalents being based on the mol of compound of formula (XXI).

When ammonia, formamide, ethyl carbamate or mixtures thereof are used asreagent (M-A), preferably from 1.0 to 100 mol equivalents, morepreferably from 1.1 to 50 mol equivalents, even more preferably from 1.1to 30 mol equivalents of ammonia, formamide, ethyl carbamate or mixturesthereof are used, the mol equivalents being based on the mol of compoundof formula (XXI).

When one or more substances selected from the group ammonia, formamideand ethyl carbamate, and one or more substances different from ammonia,formamide and ethyl carbamate are used as reagent (M-A), the givenamounts for ammonia, formamide and ethyl carbamate, and the givenamounts for the one or more substances different from ammonia, formamideand ethyl carbamate, add up to the total amount of reagent (M-A); thetotal amount of reagent (M-A) is preferably from 1.0 to 100 molequivalents, more preferably from 1.1 to 50 mol equivalents, even morepreferably from 1.1 to 30 mol equivalents, the mol equivalents beingbased on the mol of compound of formula (XXI).

Preferably from 0.01 to 15 mol equivalents, more preferably from 0.02 to10 mol equivalents, even more preferably from 0.02 to 5 mol equivalentsof compound (M-comp) are used, the mol equivalents being based on themol of compound of formula (XXI).

When reagent (M-A) is not one or more substances selected from the groupammonia, formamide and ethyl carbamate, then preferably from 1 to 15 molequivalents, more preferably from 1 to 10 mol equivalents, even morepreferably from 1 to 5 mol equivalents of compound (M-comp) are used,the mol equivalents being based on the mol of compound of formula (XXI).

Preferably, the amount of solvent (M-solv) is from 0.5 to 20 fold, morepreferably from 1 to 20 fold, even more preferably of from 2 to 20 fold,of the weight of compound of formula (XXI).

Preferably, the reaction (M1-reac) is done under inert atmosphere.

When tritylamine is used as reagent (M-A), the product of reaction(M1-reac) may be N-trityl medetomidine and the trityl residue would haveto be removed.

Preferably in this case, the method for preparation of compound offormula (XX) comprises a further step (M2); step (M2) is done after step(M1); step (M2) comprises a reaction (M2-reac);

reaction (M2-reac) is the treatment of the product of reaction (M1-reac)with an acid (M-acid detrit). Acid (M-acid detrit) is preferablyselected from the group consisting of acetic acid, propionic acid,formic acid, HCl or mixtures thereof.

Acid (M-acid detrit) can be used as an aqueous solution.

Any sequence of the reaction of reagent (M-reag) and of reagent (M-A)with the compound of formula (XXI) in reaction (M1-reac) can be used:

compound of formula (XXI) can first be reacted with reagent (M-reag) andthen reagent (M-A) added;

-   -   or

compound of formula (XXI) can first be reacted with reagent (M-A) andthen reagent (M-reag) added;

-   -   or

compound of formula (XXI) can simultaneously be reacted with reagent(M-reag) and with reagent (M-A), this embodiment is preferably suitedfor the case that reagent (M-A) and solvent (M-solv) are identical andare formamide, ethyl carbamate or acetamide; preferably formamide.

Preferably, compound of formula (XXI) is first reacted with reagent(M-reag) and then reagent (M-A) added;

-   -   or

compound of formula (XXI) is simultaneously reacted with reagent(M-reag) and with reagent (M-A).

-   Step (M1) can therefore be done in three alternatives, the three    alternatives are alternative (M1-A1), alternative (M1-A2) and    alternative (M1-A3).-   Alternative (M1-A1) comprises two consecutive steps, a first step    (M1-A1-1) and a second step (M1-A1-2);-   step (M1-A1-1) comprises a reaction (M1-A1-1);-   reaction (M1-A1-1) is a reaction of compound of formula (XXI) with    reagent (M-reag) in the presence of compound (M-comp) in solvent    (M-solv);-   step (M1-A1-2) comprises a reaction (M1-A1-2);-   reaction (M1-A1-2) is a reaction of the reaction product of reaction    (M1-A1-1) with reagent (M-A) in solvent (M-solv).-   Preferably, the reaction temperature of reaction (M1-A1-1) is from    −10 to 250° C., more preferably from 0 to 200° C., even more    preferably from 10 to 180° C.-   Preferably, the reaction temperature of reaction (M1-A1-2) is from    20 to 250° C., more preferably from 50 to 200° C., even more    preferably from 80 to 180° C.-   Preferably from 0.01 to 1 mol equivalents, more preferably from 0.02    to 1 mol equivalents, even more preferably from 0.02 to 1 mol    equivalents of compound (M-comp) are used in reaction (M1-A1-1), the    mol equivalents being based on the mol of compound of formula (XXI).-   Reaction (M1-A1-2) can be done in the presence of compound (M-comp).-   When reagent (M-A) is not one or more substances selected from the    group ammonia, formamide and ethyl carbamate, then reaction    (M1-A1-2) is preferably done in the presence of compound (M-comp);    preferably from 1 to 15 mol equivalents, more preferably from 1 to    10 mol equivalents, even more preferably from 1 to 5 mol equivalents    of compound (M-comp) are used, the mol equivalents being based on    the mol of compound of formula (XXI).-   After reaction (M1-A1-1), the reaction product of reaction (M1-A1-1)    can be isolated by standard methods such as hydrolysis, filtration,    evaporation of the volatile components, extraction, washing, drying,    concentration, crystallization, distillation, chromatography and any    combination thereof, which are known per se to the person skilled in    the art.-   The reaction product of reaction (M1-A1-1) is the compound of    formula (XXIII);

wherein

R2 is 4-tolyl, phenyl, 4-acetamidophenyl, methyl or trifluoromethyl;

preferably, R2 is 4-tolyl, which is compound of formula (23).

Compound of formula (XXIII) can be isolated after reaction (M1-A1-1) byaddition of water to the reaction mixture as obtained from reaction(M1-A1-1). The addition of water precipitates compound of formula(XXIII). Compound of formula (XXIII) can then be isolated by filtration,followed preferably by washing and drying. Compound of formula (XXIII)can be further purified by crystallization.

The volume of water used for this precipitation is preferably from 0.01to 5 fold, more preferably from 0.05 to 2 fold, of the volume of solvent(M-solv).

Alternative (M1-A2) comprises two consecutive steps, a first step(M1-A2-1) and second a step (M1-A2-2);

-   step (M1-A2-1) comprises a reaction (M1-A2-1);-   reaction (M1-A2-1) is a reaction of compound of formula (XXI) with    reagent (M-A) in solvent (M-solv);-   step (M1-A2-2) comprises a reaction (M1-A2-2).-   reaction (M1-A2-2) is a reaction of the reaction product of reaction    (M1-A2-1) with reagent (M-reag) in the presence of compound (M-comp)    in solvent (M-solv).-   Preferably, the reaction temperature of reaction (M1-A2-1) is from 0    to 250° C., more preferably from 10 to 200° C., even more preferably    from 20 to 180° C.-   Preferably, the reaction temperature of reaction (M1-A2-2) is from    −10 to 250° C., more preferably from 0 to 200° C., even more    preferably from 20 to 180° C.-   In case of reagent (M-A) not being ammonia and tritylamine, reaction    (M1-A2-1) can be done in the presence of an acid (M1-A2-1); acid    (M1-A2-1) is selected from the group consisting of p-toluenesulfonic    acid, methanesulfonic acid and benzenesulfonic acid;-   preferably from 0.01 to 1 mol equivalents, more preferably from 0.05    to 0.5 mol equivalents, even more preferably from 0.1 to 0.3 mol    equivalents of acid (M1-A2-1) are used in reaction (M1-A2-1), the    mol equivalents being based on the mol of compound of formula (XXI).-   Reaction (M1-A2-1) can be done in the presence of compound (M-comp).-   When reagent (M-A) is not one or more substances selected from the    group ammonia, formamide and ethyl carbamate, then reaction    (M1-A2-1) is preferably done in the presence of compound (M-comp);    preferably from 1 to 15 mol equivalents, more preferably from 1 to    10 mol equivalents, even more preferably from 1 to 5 mol equivalents    of compound (M-comp) are used, the mol equivalents being based on    the mol of compound of formula (XXI).-   Preferably from 0.01 to 1 mol equivalents, more preferably from 0.02    to 1 mol equivalents, even more preferably from 0.02 to 1 mol    equivalents of compound (M-comp) are used in reaction (M1-A2-2), the    mol equivalents being based on the mol of compound of formula (XXI).-   Alternative (M1-A3) comprises a step (M1-A3-1)-   step (M1-A3-1) comprises a reaction (M1-A3-1);-   reaction (M1-A3-1) is a reaction of compound of formula (XXI) with    reagent (M-reag) and with reagent (M-A) in solvent (M-solv).-   Preferably, the reaction temperature of reaction (M1-A3-1) is from 0    to 250° C., more preferably from 20 to 200° C., even more preferably    from 50 to 180° C.-   Reaction (M1-A3-1) can be done in the presence of compound (M-comp);    preferably from 1 to 15 mol equivalents, more preferably from 1 to    10 mol equivalents, even more preferably from 1 to 5 mol equivalents    of compound (M-comp) are used in reaction (M1-A3-1), the mol    equivalents being based on the mol of compound of formula (XXI).

In case of all these three alternatives, reagent (M-reag), reagent(M-A), compound (M-comp) and solvent (M-solv) are as defined herein,also with all their preferred embodiments.

When the reaction (M1-reac) is completed, the compound of formula (XX)can be isolated by standard methods such as evaporation of volatilecomponents, extraction, washing, drying, concentration, filtration,crystallization, distillation, chromatography and any combinationthereof, which are known per se to the person skilled in the art.

Preferably, the volatile components of the reaction mixture are removedby evaporation under reduced pressure.

Preferably, the reaction mixture resulting from reaction (M1-reac) orthe reaction mixture resulting from reaction (M2-reac) can be extractedwith a solvent (M-extract), solvent (M-extract) is preferably selectedfrom the group consisting of water, toluene, benzene, xylene,chlorobenzene, dichloromethane, chloroform, acetic acid C₁₋₈ alkyl esterand combinations thereof;

the acetic acid C₁₋₈ alkyl ester is preferably an acetic acid C₁₋₄ alkylester, more preferably selected from the group consisting of ethylacetate, isopropyl acetate and butyl acetate;

preferably solvent (M-extract) is selected from the group consisting oftoluene, dichloromethane, ethyl acetate, isopropyl acetate and mixturesthereof.

The extraction can be followed by filtration and concentration of theextract.

Preferably, after an extraction with a solvent (M-extract), the extractresulting from the extraction with solvent (M-extract) can be extractedwith an aqueous solution of an acid (M-acid). Acid (M-acid) ispreferably selected from the group consisting of oxalic acid, citricacid, maleic acid, fumaric acid, tartaric acid, NH₄Cl, HCl, HBr, H₂SO₄,H₃PO₄ and mixtures thereof.

The extract resulting from the extraction with an aqueous solution ofacid (M-acid) can be washed with a solvent (M-wash).

-   Preferably, solvent (M-wash) is selected from the group consisting    of toluene, benzene, xylene, chlorobenzene, dichloromethane,    chloroform, acetic acid C₁₋₈ alkyl ester and mixtures thereof; the    acetic acid C₁₋₈ alkyl ester is preferably an acetic acid C₁₋₄ alkyl    ester, more preferably selected from the group consisting of ethyl    acetate, isopropyl acetate and, butyl acetate.-   The product can be isolated by concentration of the extract that was    washed with solvent (M-wash).

In another preferred embodiment, the reaction mixture resulting fromreaction (M1-reac) or the reaction mixture resulting from reaction(M2-reac) can be, without above mentioned extraction with solvent(M-extract), acidified by mixing with an aqueous solution of acid(M-acid). The mixture, that is thereby obtained, can be washed withsolvent (M-wash), and the product can be isolated by concentration.

-   If the deprotonated medetomidine is to be isolated, a suspension or    solution of the salt of medetomidine, preferably an aqueous    suspension or solution of the salt of medetomidine, can be basified    by addition of a base (M-basify) or of an aqueous solution of base    (M-basify);-   preferably base (M-basify) is selected from the group consisting of    NaHCO₃, Na₂CO₃, NaOH and mixtures thereof.-   Preferably, base (M-basify) is added in such an amount, that the pH    of the resulting mixture is from 7 to 12, more preferably from 8 to    10, even more preferably from 8 to 9.

After the addition of base (M-basify), an aqueous phase can be extractedwith solvent (M-extract), followed by isolation of the product byconcentration of the extract.

Preferably, any washing of any organic phase after reaction (M1-reac) orafter reaction (M2-reac) can be done with water, with base (M-basify),with an aqueous solution of base (M-basify) or with brine.

Preferably, any extraction of any aqueous phase after reaction (M1-reac)or after reaction (M2-reac) is done with solvent (M-extract).

Preferably, the reaction mixture after reaction (M1-reac) or afterreaction (M2-reac) is first concentrated under reduced pressure, thendiluted with water and acidified with acid (M-acid) as described above,washed with solvent (M-wash), preferably solvent (M-wash) is toluene,basified with base (M-basify), preferably base (M-basify) is an aqueoussolution of NaHCO₃, and then extracted with solvent (M-extract),preferably solvent (M-extract) is selected from the group consisting oftoluene, dichloromethane, isopropyl acetate and ethyl acetate; followedby isolation of the product by concentration of the extract.

In another preferred embodiment, compound of formula (XX) is purifiedafter reaction (M1-reac) or after reaction (M2-reac) by chromatography.

Any organic phase can be dried, preferably over MgSO₄ or Na₂S0₄.

Any concentration is preferably done by distillation, preferably underreduced pressure.

The compound of formula (XX) can be purified, preferably bycrystallization or distillation under reduced pressure, more preferablyby crystallization from a mixture of cyclohexane and toluene, even morepreferably from cyclohexane:toluene 99:1 v/v.

The compound of formula (XX) may also be converted into a salt by mixingwith an acid (M-acid salt), acid (M-acid salt) is preferably used asaqueous solution, acid (M-acid salt) is preferably selected from thegroup consisting of acetic acid, oxalic acid, HCl and H₂SO₄; then it canbe isolated by filtration and purified by recrystallization in a solvent(M-cryst), solvent (M-cryst) is preferably selected from the groupconsisting of water, ethanol, methanol, isopropanol, acetonitrile,hexane, cyclohexane, heptane, toluene, ethyl acetate and mixturesthereof; recrystallization can be repeated using a different solvent(M-cryst).

Preferably, the acidic inorganic solid substance in the list of possiblecompounds for catalyst (N-cat) is aluminosilicate.

-   Preferably, the acidic ion exchange resin in the list of possible    compounds for catalyst (N-cat) is selected from the group consisting    of copolymers of styrene and divinylbenzene and of perfluorinated    branched or linear polyethylenes, these polymers being    functionalized with SO₃H groups;-   more preferably, the acidic ion exchange resin is selected from the    group consisting of copolymers of styrene and divinylbenzene    containing more than 5% of divinylbenzene, preferably being    macroreticular, and of perfluorinated polyethylenes, these polymers    being functionalized with SO₃H groups.-   Preferably, the inorganic acid in the list of possible compounds for    catalyst (N-cat), with which the carbon was treated, is selected    from the group consisting of HCl, H₂SO₄ and HNO₃.-   Preferably, catalyst (N-cat) is selected from the group consisting    of acetic acid, formic acid, trifluoroacetic acid, methanesulfonic    acid, p-toluenesulfonic acid, HCl, HBr, H₂SO₄, H₃PO₄, BCl₃, BF₃OEt₂,    MgCl₂, MgBr₂, AlCl₃, ZnCl₂, Cu(BF₄)₂, aluminosilicate, acidic ion    exchange resin, carbon treated with HCl, H₂SO₄ or HNO₃, and mixtures    thereof;-   more preferably, catalyst (N-cat) is selected from the group    consisting of acetic acid, formic acid, methanesulfonic acid,    p-toluenesulfonic acid, HCl, H₂SO₄, BF₃OEt₂, Cu(BF₄)₂,    aluminosilicate, acidic ion exchange resin, and mixtures thereof;-   even more preferably catalyst (N-cat) is selected from the group    consisting of methanesulfonic acid, p-toluenesulfonic acid, H₂SO₄,    BF₃OEt₂, Cu(BF₄)₂, aluminosilicate, acidic ion exchange resin, and    mixtures thereof;-   especially catalyst (N-cat) is selected from the group consisting of    methanesulfonic acid, p-toluenesulfonic acid, H₂SO₄, BF₃OEt₂ and    mixtures thereof.-   Preferably, reaction (N-reac) is done in a solvent (N-solv).-   Solvent (N-solv) is preferably selected from the group consisting of    water, tert-butanol, isopropanol, acetonitrile, propionitrile, THF,    methyl-THF, NMP, dioxane, 1,2-dimethoxyethane, dichloromethane,    1,2-dichloroethane, chloroform, toluene, benzene, chlorobenzene,    hexane, cyclohexane, ethyl acetate, acetic acid, formic acid,    trifluoroacetic acid and mixtures thereof;-   more preferably from water, acetonitrile, propionitrile, THF,    2-methyl-THF, 1,2-dimethoxyethane, dichloromethane,    1,2-dichloroethane, chloroform, toluene, cyclohexane, ethyl acetate,    acetic acid, formic acid and mixtures thereof;-   even more preferably from water, acetonitrile, propionitrile, THF,    2-methyl-THF, 1,2-dimethoxyethane, dichloromethane,    1,2-dichloroethane, toluene, ethyl acetate and mixtures thereof;-   especially from acetonitrile, THF, 2-methyl-THF, dichloromethane,    toluene, ethyl acetate and mixtures thereof.

The catalyst (N-cat) can be used in a pure form or as hydrate.

The catalyst (N-cat) can be used as a solution in solvent (N-solv).

Preferably, the molar ratio between catalyst (N-cat) and compound offormula (XXII) is from 1:1000 to 10:1, more preferably from 1:100 to5:1, even more preferably from 1:50 to 1:1, especially from 1:25 to 1:2.

Preferably, the reaction temperature of reaction (N-reac) is from −20 to200° C., more preferably from 0 to 150° C., even more preferably from 10to 100° C.

The reaction (N-reac) can be done in a system that is closed or open tothe atmosphere. In a closed system, the pressure depends mainly on theboiling point of a solvent (N-solv) and on the reaction temperature ofreaction (N-reac).

Preferably, the reaction (N-reac) is done at a pressure of from 0.01 barto 20 bar, more preferably of from 0.1 to 10 bar, even more preferablyof from atmospheric pressure to 5 bar. More preferably, the reaction(N-reac) is done in an open system.

Preferably, the reaction time of reaction (N-reac) is from 30 min to 72h, more preferably from 1 h to 48 h, even more preferably from 1.5 h to24 h.

Alternatively, reaction (N-reac) can be done as a continuous gas-phasereaction by passing the evaporated compound of formula (XXII) over thecatalyst (N-cat). This gas-phase reaction can be done in the presence ofan inert gas, the inert gas is preferably selected from the groupconsisting of nitrogen, a noble gas and carbon dioxide.

After reaction (N-reac), compound of formula (XXI) can be isolated bystandard methods such as evaporation of volatile components, extraction,washing, drying, concentration, filtration, crystallization,distillation, chromatography and any combination thereof, which areknown per se to the person skilled in the art.

Preferably, any volatile components of the reaction mixture or added orgenerated during work up can be removed by evaporation under reducedpressure.

Preferably, the reaction mixture resulting from reaction (N-reac) or anyaqueous phase during the work up after reaction (N-reac) can beextracted with solvent (M-extract), with solvent (M-extract) as definedabove, also with all its preferred embodiments.

Preferably, any washing of any organic phase after reaction (N-reac) canbe done with water, with a base (M-basify), with an aqueous solution ofa base (M-basify), with an aqueous solution of an acid (M-acid) or withbrine; with base (M-basify) and acid (M-acid) as defined above, alsowith all their preferred embodiments.

Any extraction or washing can be followed by filtration andconcentration of the extract or of the washed mixture.

In another preferred embodiment, compound of formula (XXI) is purifiedafter reaction (N-reac) by chromatography.

Any organic phase can be dried, preferably over MgSO₄ or Na₂SO₄.

Any concentration is preferably done by distillation, preferably underreduced pressure.

Compound of formula (XXI) can be obtained in step (N) as the aldehyde asdepicted in formula (XXI), but also in form of its hydrate orhemiacetal. The hemiacetal of compound of formula (XXI), which canresult as product from step (N), can be the product of an additionreaction between the aldehyde as depicted in formula (XXI) and analcohol selected from the group consisting of tert-butanol andisopropanol, or between the aldehyde as depicted in formula (XXI) andany alcohol which is used during the isolation after reaction (N-reac).Also this hydrate and this hemiacetal can be directly used in step (M1).

When compound of formula (XXI) is obtained from reaction (N-reac) inform of its hydrate or of a hemiacetal, the hydrate or the hemiacetalecan be converted into the aldehyde by standard reactions known to theperson skilled in the art.

In another preferred embodiment, compound (XXI) is not isolated afterreaction (N-reac). Preferably, reaction (N-reac) and reaction (M1-reac)are done in the same pot. More preferably, after reaction (N-reac)solvent (N-solv) is removed by evaporation, and reaction (M1-reac) isdone after evaporation of solvent (N-solv) and in the same pot asreaction (N-reac).

Preferably, R1 is Br.

-   Preferably, reagent (Q1-reag) is selected from the group consisting    of lithium, magnesium, aluminum, isopropylmagnesium chloride,    isopropylmagnesium bromide, n-butyllithium, sec-butyllithium,    tert-butyllithium, and mixtures thereof;-   more preferably, reagent (Q1-reag) is selected from the group    consisting of lithium, magnesium, isopropylmagnesium chloride,    isopropylmagnesium bromide, n-butyllithium and mixtures thereof.-   Reaction (Q1-reac) can be done in the presence of a catalyst    (Q1-cat); catalyst (Q1-cat) is selected from the group consisting of    iodine, 1,2-dibromoethane, TiCl₄, AlCl₃, PbCl₂, BiCl₃, LiCl and    mixtures thereof.-   Preferably, reaction (Q1-reac) is performed in a solvent (Q1-solv).-   Preferably, reaction (Q2-reac) is performed in a solvent (Q2-solv).-   Preferably, solvent (Q1-solv) and solvent (Q2-solv) are identical or    different and independently from each other selected from the group    consisting of THF, toluene, heptane, methylcyclohexane,    ethylcyclohexane, hexane, 2-methyl-THF, NMP, diethylether,    methyl-tert-butylether, methoxycyclopentane, diisopropylether,    2,2,5,5-tetramethyl-THF, 1,2-dimethoxyethane,    N,N,N′,N′-tetramethyl-1,2-ethylenediamine,    1,4-diazabicyclo[2.2.2]octane, tri C₁₋₄ alkyl amine and mixtures    thereof;-   more preferably from the group consisting of THF, toluene, heptane,    hexane, 2-methyl-THF, 1,2-dimethoxyethane, methyl-tert-butylether,    methoxycyclopentane, tri C₁₋₄ alkyl amine and mixtures thereof;-   even more preferably from the group consisting of THF, toluene,    heptane, hexane, 2-methyl-THF, 1,2-dimethoxyethane, triethylamine    and mixtures thereof.

When heptane is used as solvent, it is often used as a mixture ofisomeric heptanes.

In one particular embodiment, solvent (Q1-solv) is THF, hexane or amixture thereof, and solvent (Q2-solv) is THF, hexane, toluene or amixture thereof.

In another particular embodiment, solvent (Q1-solv) and solvent(Q2-solv) are identical. The reaction temperatures of reaction (Q1-reac)and of reaction (Q2-reac) are identical or different and independentlyfrom each other preferably from −100 to 150° C., more preferably from−90 to 100° C., and even more preferably from −80 to 80° C.

Reaction (Q1-reac) and reaction (Q2-reac) can be done at a constanttemperature, or the temperature may be modified during the progress ofthe reactions. For instance, the reactions can run for a certain time atfirst temperature, and then for a subsequent time at a secondtemperature different from the first temperature. Alternatively, thetemperature may be modified continuously during the reaction.

The reaction times of reaction (Q1-reac) and of reaction (Q2-reac) areidentical or different and independently from each other preferably from30 min to 48 h, more preferably from 1 to 24 h, even more preferablyfrom 2 to 12 h.

The amounts of solvent (Q1-solv) and of solvent (Q2-solv) are identicalor different and independently from each other preferably from 2 to 40fold, more preferably from 3 to 20 fold, even more preferably from 5 to10 fold, of the weight of compound of formula (XXV) in case of solvent(Q1-solv), and of the weight of the reaction product of reaction(Q1-reac) in case of solvent (Q2-solv).

Preferably, from 1.0 to 10 mol equivalents, more preferably from 1.1 to5 mol equivalents, even more preferably from 1.1 to 3 mol equivalents ofreagent (Q1-reag) are used, the mol equivalents being based on the molof compound of formula (XXV).

Preferably, from 1.0 to 10 mol equivalents, more preferably from 1.1 to5 mol equivalents, even more preferably from 1.1 to 3 mol equivalents ofchloroacetone are used, the mol equivalents being based on the mol ofcompound of formula (XXV).

Preferably, reaction (Q1-reac) and reaction (Q2-reac) are done atatmospheric pressure.

Preferably, reaction (Q1-reac) and reaction (Q2-reac) are done underinert atmosphere.

Preferably, the inert atmosphere is achieved by the use if an inert gaspreferably selected from the group consisting of argon, another noblegas, lower boiling alkane, nitrogen and mixtures thereof.

The lower boiling alkane is preferably a C₁₋₃ alkane, i.e. methane,ethane or propane.

After reaction (Q2-reac), compound of formula (XXII) can be isolated bystandard methods such as evaporation of volatile components, extraction,washing, drying, concentration, crystallization, distillation,chromatography and any combination thereof, which are known per se tothe person skilled in the art.

Preferably, the reaction product of reaction (Q1-reac) is not isolated.

Preferably, reaction (Q1-reac) and reaction (Q2-reac) are doneconsecutively.

Preferably, reaction (Q1-reac) and reaction (Q2-reac) are done in onepot.

In another preferred embodiment, reaction (Q1-reac) and reaction(Q2-reac) can be done in one pot by adding reagent (Q1-reag) to amixture of compound of formula (XXV) and chloroacetone in a solvent(Q1-solv).

Preferably, for the isolation of compound of formula (XXII) afterreaction (Q2-reac), a reagent (Q3) is combined with the reaction mixturederived from reaction (Q2-reac);

-   reagent (Q3) is selected from the group consisting of water,    methanol, ethanol, oxalic acid, citric acid, NH₄Cl, HCl, HBr, HNO₃,    H₂SO₄, H₃PO₄, acetic acid, propionic acid, formic acid and mixtures    thereof.

Preferably, reagent (Q3) is water or aqueous NH₄Cl;

more preferably, reagent (Q3) is water.

Preferably, from 0.01 to 1000 mol equivalents, more preferably from 0.02to 1000 mol equivalents, of reagent (Q3) are used, the mol equivalentsbeing based on the mol of compound of formula (XXV). Reagent (Q3) isused to neutralize any excess of reagent (Q1-reag), therefore the amountof reagent (Q3) is adjusted with respect to the excess of reagent(Q1-reag) used in reaction (Q1-reac).

Compound of formula (XXII) is preferably isolated using conventionalmethods, such as evaporation of volatile components, hydrolysis andoptional acidification of the higher-boiling residue, extraction, anddistillation.

The compound of formula (XXII) can be purified, preferably bycrystallization or distillation under reduced pressure.

Any extraction of an aqueous phase is done preferably with a solvent(Q-extract), solvent (Q-extract) is benzene, toluene, ethyl acetate orisopropyl acetate.

Any organic phase can be dried, preferably with magnesium sulphate.

Any concentration is preferably done by distillation, preferably underreduced pressure.

Compounds of formula (XX), (XX-T), (XXI), (XXII), (XXIII) and (23) arechiral compounds, and the formulae comprise any enantiomer as well asany mixture of enantiomers of the compounds of formula (XX), of formula(XX-T), of formula (XXI), of formula (XXII), of formula (XXIII) or offormula (23) respectively.

Enantiomers can be separated by conventional procedure known in organicchemistry, such as repeated crystallizations of the (+) tartaric acidsalt in alcoholic media, as disclosed for compound of formula (XX) inCordi et al., Synth. Commun. 1996, 26, 1585-1593.

Compounds of formula (XXV) are known compounds and can be preparedaccording to known methods.

The progress of any of the reactions reaction (M1-reac), reaction(N-reac), reaction (Q1-reac) and reaction (Q2-reac) can be monitored bystandard techniques, such as nuclear magnetic resonance spectroscopy(NMR), infrared spectroscopy (IR), High performance LiquidChromatography (HPLC), Liquid Chromatography Mass Spectrometry (LCMS),or Thin Layer Chromatography (TLC), and work-up of the reaction mixturecan start, when the conversion of the starting material exceeds 95%, orwhen no more starting material can be detected. The time required forthis to occur will depend on the precise reaction temperature and theprecise concentrations of all reagents, and may vary from batch tobatch.

In general, any organic phase can be dried, preferably over MgSO₄ orNa₂SO₄, if not stated otherwise.

Further subject of the invention is a compound of formula (XXIII).

Further subject of the invention is a compound of formula (23).

-   Further subject of the invention is the use of compound of    formula (XXIII) for the preparation of compound of formula (XX).-   Further subject of the invention is the use of compound of    formula (XXI) for the preparation of compound of formula (XXIII) or    for the preparation of compound of formula (XX).-   Further subject of the invention is the use of compound of    formula (XXII) for the preparation of compound of formula (XXI).-   Further subject of the invention is the use of compound of    formula (XXV) for the preparation of compound of formula (XXII).

Compared to prior art, the method of the present invention offersseveral advantages: Importantly, the whole carbon framework of compoundof formula (XX) is built in few chemical steps, using cheap reagentsonly. The few chemical steps obviously provide for a cost effectiveprocedure. No protecting groups are needed and the overall amount ofmaterial used is therefore reduced, the batch size based on molaramounts is increased.

In particular no trityl or acetale protection groups are used and noprotection of the imidazoles is necessary. Thereby the number and amountof reagents needed is reduced, and no protecting or deprotecting stepsbeing needed the waste is reduced, contrary to when for example a tritylor acetale protecting group is used. The method has good yields.

EXAMPLES

Methods

¹H and ¹³C NMR spectra were recorded on a Varian VNMRS 500 (500 MHz for¹H and 125 MHz for ¹³C) instruments in CDCl₃. Chemical shifts areexpressed in parts per million referred to TMS and coupling constants(J) in Hertz.

EI means Electron ionization mass spectra (70 eV), they were obtained onan AMD-604 spectrometer.

ESI means Electron spray ionization mass spectra

In example 1 the THF was not dried with sodium. In example 2 NaH wasused for this purpose.

Example 1 2-(2,3-Dimethylphenyl)methyloxirane, Compound of Formula(XXII), Metallation with Butyllithium in THF

To a solution of 1-bromo-2,3-dimethylbenzene (0.27 ml, 2.0 mmol) in THF(4.0 ml) at −78° C. was added n-butyllithium (2.0 ml of a 1.6 M solutionin hexane, 3.2 mmol). The mixture was stirred at −78° C. for 30 min, andthen a solution of chloroacetone (0.24 ml, 3.0 mmol) in toluene (0.42ml) was added drop wise within 20 min. The mixture was stirred at −78°C. for 1 h, and then allowed to warm to room temperature. Analysis of asample after 3 h at room temperature indicated that the title epoxidewas the main reaction product. After stirring at room temperature for 3days the mixture was poured into water (20 ml), and the product wasextracted with ethyl acetate (1×10 ml, 2×5 ml). The combined extractswere dried with MgSO₄, and concentrated under reduced pressure to yieldthe title epoxide as an oil in quantitative yield.

¹H NMR: 1.59 (s, 3H), 2.28 (s, 3H), 2.31 (s, 3H), 2.83 (br d, J=5.4,1H), 2.98 (d, J=5.4 Hz, 1H), 7.08 (m, 2H), 7.21 (m, 1H).

MS (EI): 162, 147, 133, 117 (100).

Example 2 2-(2,3-Dimethylphenyl)methyloxirane, Compound of Formula(XXII), Metallation with Magnesium in THF

To a suspension of magnesium (89 mg, 3.66 mmol) in THF (4.0 ml) wereadded NaH (81 mg, 60% in oil, 2.0 mmol), and after stirring at roomtemperature for 10 min, 1-bromo-2,3-dimethylbenzene (0.40 ml, 2.96mmol). An exothermic reaction ensues, and the resulting mixture isstirred at room temperature for 1 h. The mixture is then cooled to −20°C., and a solution of chloroacetone (0.26 ml, 3.3 mmol) in toluene (0.63ml) is drop wise added within 10 min. The mixture is then stirred atroom temperature for 2 h. A sample was worked up by mixing with water,extraction with ethyl acetate, and evaporation of the ethyl acetate witha stream of nitrogen. Analysis of the residue by 1H NMR indicated it tobe a mixture of xylene and the title oxirane.

Example 3 2-(2,3-Dimethylphenyl)propanal, Compound of Formula (XXI)

2-(2,3-Dimethylphenyl)methyloxirane, compound of formula (XXII),prepared according to example 1 (158 mg, 0.97 mmol), was dissolved intoluene (1.57 mL) and BF₃OEt₂ (0.006 ml, 0.05 mmol) was added at roomtemperature. After 2 h at room temperature, a sample was mixed withsolid NaHCO₃, filtered, concentrated under reduced pressure, and theresidue was analyzed by 1H NMR. The crude product consisted essentiallyof pure 2-(2,3-dimethylphenyl)propanal.

¹H NMR: 1.40 (d, J=7.1 Hz, 3H), 2.25 (s, 3H), 2.32 (s, 3H), 3.89 (qd,J=7.1, 1.0 Hz, 1H), 6.89 to 6.92 (m, 1H), 7.12 (m, 2H), 9.67 (d, J=1.0Hz, 1H).

Example 4 5-(1-(2,3-dimethylphenyl)ethyl)-4-tosyl-4,5-dihydrooxazole,Compound of Formula (23)

To a solution of compound of formula XXII (2.07 g, 12.8 mmol) indichloromethane (10 ml) was added BF₃OEt₂ (0.1 molar in Et₂O, 4 ml, 0.4mmol) within 4 h at room temperature. The mixture was stirred at roomtemperature for 1 h, and the solvent (dichloromethane) was thenevaporated under reduced pressure. The residue was dissolved in methanol(10 ml), and TosMIC (toluenesulfonylmethylisocyanide; 2.24 g, 11.5 mmol)and then Na₂CO₃ (102 mg, 0.96 mmol) were added. The mixture was stirredat room temperature for 1 h, and then diluted with water (5 ml). Themixture was stirred at room temperature for further 30 min, and thenkept at 4° C. overnight. Filtration and drying yielded 3.1 g (75%) ofcompound of formula (23).

¹H NMR (CDCl₃, 500 MHz): 1.28 (d, J=7 Hz, 3H), 2.23 (s, 3H), 2.30 (s,3H), 2.44 (s, 3H), 3.28 (m, 1H), 4.79 (m, 1H), 5.20 (m, 1H), 7.04 (s,1H), 7.10 (m, 3H), 7.33 (d, J=8 Hz, 2H), 7.73 (d, J=8 Hz, 2H).

Example 5 Medetomidine, Compound of Formula (XX)

Compound of formula (23) (3.16 g, 8.84 mmol), prepared according toexample 4, was dissolved in ammonia-saturated ethanol (40 ml, containingapproximately 160 mmol ammonia) and heated to 110° C. for 3 h. Themixture was then evaporated to dryness, and the residue was mixed withan aqueous, saturated solution of NaHCO₃ (20 ml). The mixture wasextracted with toluene (2×20 ml), and the combined extracts were washedwith water (2×20 ml). The combined extracts were then extracted with 10%aqueous HCl (3×20 ml), and the combined acidic extracts were basifiedwith gaseous ammonia, and extracted with toluene (2×20 ml). The combinedorganic extracts were dried over Na₂SO₄, and concentrated under reducedpressure, to yield compound of formula (XX) (1.57 g, 89%).

¹H NMR: 1.56 (d, J=7.2 Hz, 3H), 2.18 (s, 3H), 2.25 (s, 3H), 4.35 (q,J=7.2 Hz, 1H), 6.66 (s, 1H), 6.93 (dd, J=6.6, 2.2 Hz, 1H), 6.99 to 7.05(m, 2H), 7.30 (d, J=1.1 Hz, 1H), 9.84 (broad s, 1H).

¹³C NMR: 14.65, 20.72, 20.88, 14.12, 117.61, 124.62, 125.53, 127.91,134.05, 134.60, 136.76, 141.11, 143.23.

MS (ESI): 201 [M+H]⁺

This product was redissolved in acetonitrile (10 ml), and converted intoa hydrochloride salt with concentrated aqueous hydrochloric acid (0.8ml). The mixture was concentrated to dryness, and the residue wassuspended in diethylether (30 ml), and stirred at room temperatureovernight. Filtration and drying under reduced pressure yielded 1.55 g(74%) of compound of formula (XX) as hydrochloride salt.

The invention claimed is:
 1. A compound of formula (XXIII),

wherein R2 is 4-tolyl, phenyl, 4-acetamidophenyl, methyl ortrifluoromethyl.
 2. The compound according to claim 1, wherein R2 is4-tolyl.